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Radiology > Radiation Biology > Flashcards

Radiation Biology Flashcards

1
Q

radiation biology

A

portion of science which studies the effects of ionizing radiation on living organisms

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2
Q

how do we know that radiation affects living organisms

A

early pioneers
1925 factory workers
nuclear bomb
spills and disasters

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3
Q

two mechanisms of radiation injury

A

ionization
free radical formation

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4
Q

ionization

A

results in formation of a positive atom and dislodged negative electron
dislodged electron interact with other atoms within tissues

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5
Q

compton scatter

A

when an x-ray photon collides with an outer-shell electron and ejects the electron from its orbit

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6
Q

formation of free radicals

A

x-ray photons ionizes H2O
hydrogen and hydroxyl free radicals

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7
Q

what is a free radical

A

an uncharged atom that exists with a single unpaired electron in its outermost shell: reactive and unstable

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8
Q

formation of free radicals Part A

A

x-ray photons interact with water in cells
ionization occurs
resulting in free radical formation

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9
Q

formation of free radicals Part B

A

free radicals
combine to form
toxins such as H2O2 (hydrogen peroxide)

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10
Q

damage to living tissue caused by exposure to ionizing radiation may result from

A

a direct hit and absorption of an x-ray photon within a cell
absorption of an x-ray photon by water within a cell accompanied by free radical formation

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11
Q

theories of radiation injury

A

direct theory and indirect theory

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12
Q

direct theory

A

cell damage results when ionizing radiation directly hits critical area within the cell
occurs infrequently

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13
Q

indirect theory

A

x-rays photons are absorbed within the cell and cause the formation of toxins which damage the cell
-when photons are absorbed by water within a cell, free radical formation results
-free radicals combine to form toxins that damage cells

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14
Q

dose-response curve

A

used to correlate the damage of tissue with the does of radiation received
liner nonthreshold relationship

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15
Q

stochastic radiation effects

A

direct function of the dose
no dose threshold; effects do not depend on magnitude of absorbed does

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16
Q

nonstochastic radiation effects

A

have a threshold and increase severity with increasing absorbed dose
occur after threshold of exposure has been exceeded
cause significant cell damage

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17
Q

sequence of radiation injury

A

latent period: time between exposure and observable clinical signs, depends of dose of radiation
period of injury: a variety of cellular injuries may result
recovery period: cells can repair the damage caused by radiation
cumulative effects: effects of radiation exposure are additive, unrepaired damage accumulates in tissues

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18
Q

determining factors of radiation injury

A

total dose
dose rate
amount of tissue irradiated
cell sensitivity
age

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19
Q

short term effects

A

not applicable to dentistry

20
Q

long term effects

A

small doses absorbed over a long period of time
effects seen after years, decades, generations

21
Q

somatic effects

A

all cells in body except reproductive cells
produce poor health in irradiated individual
cancer, leukemia, cataracts

22
Q

genetic effects

A

reproductive cells
not seen in exposed individual
passed on to future generations
genetic damage cannot be repaired

23
Q

radiosensitive cells

A

blood cells
immature reproductive cells
young bone cells
small lymphocyte

24
Q

radioresistant cells

A

bone cells
muscle cells
nerve cells

25
Q

radiosensitive organs

A

lymphoid tissues
bone marrow
testes
intestines

26
Q

radioresistant organs

A

salivary glands
kidney
liver

27
Q

critical organs

A

an organ that, if damaged, diminishes the quality of a person’s life
skin thyroid gland, lens of the eye, bone marrow

28
Q

units of measurement

A

exposure
dose
dose equivalent

29
Q

traditional system units of radiation measurement

A

roentgen
radiation absorbed dose (rad)
roentgen equivalent (in) man (rem)

30
Q

SI system (newer) units of radiation measurement

A

coulombs/kilogram (C/kg)
gray (Gy)
sievert (Sv)

31
Q

exposure measurement

A

measurement of ionization in the air produced by x-rays

32
Q

roentgen measurement

A

measures radiation by determining the amount of ionization that occurs in air
does not describe amount of radiation absorbed

33
Q

no SI equivalent

A

exposure is stated in coulombs per kilogram (C/kg)

34
Q

dose measurement

A

unit is the rad (radiation absorbed dose)
amount of energy absorbed by tissue

35
Q

dose equivalent measurement

A

used to compare the biological effects of different types of radiation
the roentgen equivalent in man (rem) and the sievert (Sv)

36
Q

rem

A

the product of absorbed dose (rads) and a quality factor (QF) specific for the type of radiation

37
Q

natural background radiation

A

form of ionizing radiation that is ubiquitous in the environment
-cosmic radiation
-terrestrial radiation
-ingestion
-inhalation

38
Q

artificial or human-made radiation

A

resulting from modern technology

39
Q

risk and risk estimate

A

likelihood of adverse effects or death resulting from exposure
death is more likely to occur from common activities than from dental imaging procedures

40
Q

thyroid gland risk elements

A

primary beam does not irradiate the thyroid gland, but thyroid radiation exposure does occur
6000 mrad to produce cancer in thyroid gland

41
Q

bone marrow risk elements

A

areas of maxilla and mandible exposed is small percentage of active bone marrow
does of 5000 mrad or more

42
Q

skin cancer risk elements

A

more than 500 dental radiographs in a 14-day period would have to be exposed to cause erythema

43
Q

eyes risk elements

A

more than 200,000 mrad for cataract formation

44
Q

receptor choice

A

reduced 50-90% when using digital sensors when compared to film

45
Q

collimation

A

rectangular collimation reduces by 60-70%

46
Q

technique patient exposure and dosage

A

limited by increasing source-receptor distance/long cone
paralleling technique and increase source-receptor distance reduces the skin dose

Radiology (16 decks)

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